Immediate response steam generating system and method

Abstract

The method of generating immediate and thereafter continuous steam is used in a steam generating system comprising a steam accumulator, a steam outlet connected to the steam accumulator, an outlet valve at the steam outlet, and a quick response steam generator unit connected to the steam accumulator. The method comprises the steps of providing latent steam in the steam accumulator, opening the outlet valve to allow latent steam in the steam accumulator to exit through the steam outlet, feeding water to the steam generator unit, heating the water fed to the steam generator unit while the latent steam exits through the steam outlet and, before the latent steam has entirely exited the steam accumulator, generating steam with the steam generator unit to feed the steam accumulator and controlling the steam flow rate through the steam outlet to maintain it at a value which is essentially not greater than the steam flow rate from the steam generator unit to the steam accumulator. The steam generating system is capable of generating immediate and thereafter continuous steam from an initial steam generator unit cold condition due to the steam accumulator providing steam at the steam outlet while the steam generator unit heats the water fed therein.

The invention claimed is: 
     
       1. A method of generating immediate and thereafter continuous steam in an auxiliary steam generating system backing-up a main steam system having a main steam temperature and pressure, the auxiliary steam generating system comprising a steam accumulator, a steam outlet connected to said steam accumulator, an outlet valve at said steam outlet connected to the main steam system, and a quick response steam generator unit connected to said steam accumulator, said method comprising the following steps:
 providing a latent steam in said steam accumulator at an idle pressure and a temperature higher than that of the main steam system; 
 opening said outlet valve when the immediate and thereafter continuous steam is requested from the main steam system, to allow the latent steam in said steam accumulator to exit through said steam outlet towards the main steam system, the latent steam becoming the immediate and thereafter continuous steam; 
 feeding water to said steam generator unit, wherein water fed to said steam generator unit is fed from said steam accumulator; 
 heating the water fed to said steam generator unit that exits the steam generator unit as liquid-state water that flashes and becomes latent steam in the accumulator, the latent steam exiting through said steam outlet as the immediate and thereafter continuous steam and the steam generator unit comprises at least one coil boiler comprising coil-shaped pipes in which the water fed is circulated and from 3% to 30% by mass of the water fed to the at least one coil boiler exits as steam; and 
 before said latent steam has entirely exited said steam accumulator as the immediate and thereafter continuous steam, controlling the steam flow rate through said steam outlet to maintain the steam flow rate at a value which is essentially not greater than the steam flow rate from said steam generator unit to said steam accumulator; 
 thereby said auxiliary steam generating system generates immediate and thereafter continuous steam from an initial steam generator unit cold condition due to said steam accumulator providing steam at said steam outlet while said steam generator unit heats the water fed therein, and 
 wherein the steam generator unit generates steam from the initial steam generator unit cold condition to a full steam production mode of the steam generator unit in 5 to 10 minutes and to maintain the main steam system at the main steam temperature and pressure. 
 
     
     
       2. A method of generating immediate and thereafter continuous steam as defined in  claim 1 , wherein said idle pressure and temperature in said steam accumulator are maintained by inputting steam through an auxiliary steam line. 
     
     
       3. A method of generating immediate and thereafter continuous steam as defined in  claim 1 , wherein a water input line is further connected to said steam accumulator to feed water to said steam accumulator, whereby water fed to said steam generator unit is preheated by its passage through said steam accumulator. 
     
     
       4. A method of generating immediate and thereafter continuous steam as defined in  claim 1 , wherein most of the water mass circulated through said coil-shaped pipes is maintained in liquid-state even when steam is generated by said coil boiler. 
     
     
       5. A method of generating immediate and thereafter continuous steam as defined in  claim 4 , wherein between 70% and 97% of the water mass circulated through said coil-shaped pipes is maintained in liquid-state even when steam is generated by said coil boiler. 
     
     
       6. An auxiliary steam generating system for generating steam to back-up a main steam system having a main steam temperature and pressure, auxiliary steam generating system comprising:
 a steam accumulator at an idle pressure and temperature higher than that of the main steam system, the steam accumulator having a steam outlet; 
 a quick-response steam generator unit connected to said accumulator wherein water is fed from the steam accumulator to the steam generator and exits a liquid-state water from said steam generator unit and is returned to said steam accumulator; 
 a steam outlet valve at said steam outlet connected to the main steam system, controlling the steam flow rate out of said steam accumulator, the outlet valve opens when the steam to back-up the main steam system is requested, and 
 the steam generator unit comprises at least one coil boiler comprising coil-shaped pipes in which the water fed is circulated and from 3% to 30% by mass of the water fed to the at least one coil boiler exits as liquid-state water; and 
 a steam generator unit water inlet connected to said steam accumulator; wherein said auxiliary steam generating system is capable of generating immediate and thereafter continuous steam from an initial steam generator unit cold condition due to said steam accumulator providing steam at said steam outlet while said steam generator unit heats the water fed therein and the auxiliary steam generating system generating steam at a steam flow rate through said steam outlet valve at a value which is essentially not greater than the steam flow rate from said steam generator unit to said steam accumulator, and 
 wherein the steam generator unit generates steam from the initial steam generator unit cold condition to a full steam production mode of steam generator unit in 5 to 10 minutes, and to maintain the main steam system at the main steam temperature and pressure. 
 
     
     
       7. A steam generating system as defined in  claim 6 , wherein said steam accumulator comprises an idle pressure/temperature maintaining device. 
     
     
       8. A steam generating system as defined in  claim 7 , wherein said idle pressure/temperature maintaining device includes an auxiliary steam line connected to a steam source, said auxiliary steam line having a steam inlet connected to said steam accumulator for allowing steam to be injected into said steam accumulator. 
     
     
       9. A steam generating system as defined in  claim 6 , wherein said steam generator unit water inlet is connected to said steam accumulator, and said steam generating system comprises a system water inlet connected to said steam accumulator for feeding water thereto, whereby the water fed to said steam generator unit is first mixed with water from the said steam accumulator.